1. Field of the Invention
The present invention relates to railway cars and more particularly relates to a rotary dump gondola car having a continuous center sill with a depressed or drop center portion between the wheel assemblies.
2. Description of the Prior Art
Drop center rotary dump gondola cars are known in the art as evidenced by U.S. Pat. No. 3,713,400 which issued to Teoli on Jan. 30, 1973. This patent discloses a drop center car which includes end stub center sills and box side sills. The drop center portion is formed from a parabolic plate which is attached to the side sills and to end sheets. However, no center sill is provided in the drop center portion, and accordingly the side sills and side walls must support substantially all of the vertical and longitudinal loads applied to the car. Accordingly, the bolsters and side sills must be of rather heavy rigid construction. Also, the parabolic shape of the drop center portion somewhat limits the available space for carrying bulk commodities as compared to a flat bottom wall that extends transversely substantially the full width of the car.
U.S. Pat. No. 1,531,761, Seiders, which issued on Mar. 31, 1925 discloses a gondola car having a continuous center sill disposed within the cargo space and having cross bearers and gussets connecting flat side walls to the center sill. However, the center sill does not include a depressed portion but is positioned in its entirety above the level of the trucks. Accordingly, the car has a high center of gravity, and does not include a drop center portion.
U.S. Pat. No. 3,240,168 which issued on Mar. 15, 1966 to Charles et al discloses a gondola car with a depressed center, or pocket, between the wheels for lowering the center of gravity of the car. The car is also adapted for rotary unloading. This patent discloses cross members which prevent the lateral movement of the side cord. However, the drop center portion of the car does not include a center sill, but instead, relies on external channel stiffeners for supporting the vertical load from the side walls and channel side sills. Thus, the bolsters and channel side sills must be rather sturdy to support the longitudinal and vertical forces applied thereto.